The present invention relates to aqueous compositions that are especially suitable for cleaning surfaces and particularly for cleaning glass substrates and photomasks. The present invention is particularly useful for cleaning chromium photomasks and glass substrates including those for use in fabricating flat panel and liquid crystal displays.
In the fabrication of integrated circuits, one of the more critical procedures is the photolithographic processing. One of the most important aspects of photolithography processes used in the semiconductor industry is providing for defect-free photomasks.
Photomasks are used to project images onto wafer surfaces that ultimately define the regions for diffusions and implants of the doped regions, placements of interconnect lines, gates and metallizations, and locations of underlying bonding pads. The cleanliness of the photomask is extremely important. Particles left on the photomask prevent light exposure to the photoresist or cause light diffraction which may lead to defects in the final pattern.
Proper cleaning of the mask to remove unwanted particles is an integral part of mask making. One cleaning step currently used in photomask making comprises rinsing the mask with ammonium hydroxide. However, it has been observed that the ammonium hydroxide solution could stand improvement in its ability to wet the photomask and therefore ability to clean the photomask. This need is especially pronounced when dealing with chromium plated photomasks. Chromium plated photomasks are among the more important commercially employed photomasks.
Another concern with chromium photomasks is the need to avoid oxidants such as H2O2 in any cleaning solution for such since oxidants tend to cause etching of chromium and other metallic surfaces. The chromium photomasks comprise chromium coated on a glass substrate. Therefore, any cleaning solution used should not adversely effect the glass substrate and desirably also clean it.
Accordingly, room exists for improving the cleaning of photomasks.
Moreover, glass substrates used for fabricating flat panel displays such as liquid crystal displays must be properly cleaned and free from unwanted particles.
Therefore, a need also exists for improved cleaning of glass substrates.
The present invention relates to a composition which exhibits enhanced ability to clean various substrates including glass surfaces and photomasks.
More particularly, the present invention relates to an aqueous composition which comprises ammonium hydroxide in an amount of about 1 to about 30% by weight calculated as NH3 and a surface active agent represented by the formula
XF2C(CFY)nSO3A
wherein
X=F, OH or SO3A;
Y=F, H, OH or may be omitted thereby creating a double bond;
n=1-12;
A=NH4+, H+, Na+, K+, Li+, R+ or organic amine cation and R is 1-4 straight chain alkyl group;
and wherein the fluoroalkyl group is a linear group; and wherein the surface active agent is present in an amount of about 5 ppm to about 2000 ppm.
Another aspect of the present invention relates to a method for cleaning a substrate. The method comprises contacting the substrate with an aqueous composition comprising ammonium hydroxide in an amount of about 1 to about 30% by weight calculated as NH3 and a surface active agent represented by the formula
XF2C(CFY)nSO3A
wherein
X=F, OH or SO3A;
Y=F, H, OH or may be omitted thereby creating a double bond;
n=1-12;
A=NH4+, H+, Na+, K+, Li+, R+ or organic amine cation and R is 1-4 straight chain alkyl group;
and wherein the fluoroalkyl group is a linear group; and wherein the surface active agent is present in an amount of about 5 ppm to about 2000 ppm.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.